Heat exchanger

ABSTRACT

A heat exchanger, in particular an exhaust gas cooler or charge air cooler, is provided that includes a plate stack which has a plurality of elongated plate pairs, each set of two interconnected plates forming a respective second fluid channel between themselves, and a first fluid channel being formed between two plate pairs, a first fluid channel being surrounded by two second fluid channels, each second fluid channel being connected to at least one manifold.

This nonprovisional application is a continuation of InternationalApplication No. PCT/EP2013/066289, which was filed on Aug. 2, 2013, andwhich claims priority to German Patent Application No. 10 2012 216589.4, which was filed in Germany on Sep. 17, 2012, and which are bothherein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a heat exchanger, particularly a charge aircooler or an exhaust gas cooler for a motor vehicle.

2. Description of the Background Art

An exhaust gas heat exchanger, which consists of a stack surrounded by ahousing, is known from EP 1 348 924 B1, which corresponds to U.S. Pat.No. 6,920,918, whereby the stack is formed of flat tubes and each flattube contains a turbulator, whereby the exhaust gas flows through eachflat tube. A coolant channel, designed with flow directing elementsthrough which the coolant taking up the heat of the exhaust gas isconducted, is formed in each case between two flat tubes.

To be able to better compensate rising exhaust gas temperatures, anexhaust gas heat exchanger is known from DE 10 2006 005 362, whichcorresponds to U.S. Pat. No. 8,020,610, in which the flow directingelements consist of a corrugated plate. Channels with inlets andoutlets, which extend in the longitudinal or transverse direction of theexhaust gas heat exchanger, are formed in this plate. In both solutions,the exhaust gas channels are surrounded by a coolant-conducting housing,which has a substantial weight and contributes greatly to the costduring the production of the exhaust gas heat exchanger.

EP 1 762 807 B1, which corresponds to US 2007/0023174, discloses a heatexchanger with plate pairs each forming a fluid channel, whereby exhaustgas flows through the fluid channel. Individual channels which conductthe coolant are formed between the plate pairs, whereby the fluidchannels conducting the exhaust gas delimit the heat exchanger outwardlyand thus the hot fluid channels form the outer wall of the heatexchanger. To realize the coolant-conducting fluid channels laterallyoutward, embossings, which reduce the flow cross section of the exhaustgas-conducting fluid channel, are necessary in the exhaustgas-conducting wall regions of the fluid channel.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a heatexchanger that has a high thermal capacity despite minimized materialcosts and weight.

An exemplary embodiment of the invention relates to a heat exchanger,particularly an exhaust gas cooler or charge air cooler, comprising aplate stack having a plurality of elongated plate pairs, whereby in eachcase two interconnected plates form a second fluid channel between themand a first fluid channel is formed between two plate pairs, whereby afirst fluid channel is surrounded by two second fluid channels, wherebyeach second fluid channel is connected to at least one fluid collectingchannel. It is achieved thereby that the second fluid channel delimitsthe plate stack outwardly and thus the channel conducting the secondmedium and having the lower temperatures delimits the plate stackoutwardly.

In an embodiment, the interconnected two plates of a plate pair can forma U-shaped second fluid channel or a Z-shaped second fluid channelbetween them. Thus, a first fluid channel enclosed by second fluidchannels can be created by stacking two plate pairs on top of oneanother.

In an embodiment, the U-shaped second fluid channel can be covered by afurther second fluid channel such that a first fluid channel is locatedbetween the two second fluid channels.

In an embodiment, the first fluid channel can be enclosed on four sidesby the second fluid channel.

In an embodiment, a wall of the second fluid channel can delimit theheat exchanger outwardly.

In an embodiment, the two interconnected plates of a plate pair can besoldered or welded on both sides at their rims along their longitudinalextension and/or transverse extension.

In an embodiment, a rim, that can be formed perpendicular on the bottomplate and/or on the top plate, is soldered to a base of the overlyingbottom plate.

In an embodiment, at least one opening for connecting the second fluidchannel to the coolant collecting channel can be formed in at least oneof the shaped rims.

In an embodiment, the header can extend to thereby cover the plate stackapproximately perpendicularly, and can have a recess for exchanging thesecond fluid, such as a coolant, preferably opposite to the openings ofthe plate stack.

In an embodiment, the header can be formed as a tube segment. A simplefabrication can be achieved thereby.

In an embodiment, the header can encompass the plate stack at leastpartially as a tensioning clamp.

In an embodiment, one opening each can be formed in the rim of the platenear an inlet and outlet for the first fluid, whereby the inlet andoutlet for the first fluid are formed by the narrow sides of the twointerconnected plates and the openings of a plurality of interconnectedplate pairs, arranged lying on top of one another, lie approximately oneabove the other.

In an embodiment, a rimless or rimmed cover plate can be provided forclosing the topmost second fluid channel. In this case, it can beadvantageous further if a rimless or rimmed base plate is used forclosing the lowermost second fluid channel.

In an embodiment, the coolant collecting channel can be formed as aheader. As a result, in an exemplary embodiment an additional pipe forthe coolant can be omitted completely or at least partially.

In an embodiment, the header can extend covering the plate stackapproximately perpendicularly and has a recess for exchanging the secondfluid, such as a coolant, preferably opposite to the openings of theplate stack.

In an embodiment, the header can be formed as a tube segment.

In an embodiment, the header can encompass the plate stack at leastpartially as a tensioning clamp. As a result, the header has a furthereffect for holding together the plate stack.

In an embodiment, the coolant collecting channel can be formed as acoolant tank.

In an embodiment, each second fluid channel can be connected to thecoolant tank, whereby the coolant tank has an outer connection for aconnector, for example a tube, for supplying the coolant to the coolanttank or for discharging the coolant from the coolant tank. This has theadvantage that the connector can be soldered concurrently and thefabrication cost is reduced thereby. The use of a tube as a connector isfurthermore cost-effective and can be formed very flexible.

In an embodiment, the coolant tank can be formed as a one-piecediffuser. This has the advantage that a precise shaping is madepossible, because there are no or only minor distortions of anadditional joining process, particularly no welding distortions.

In an embodiment, the coolant collecting channel can be shaped as aflange, which is formed from a metal sheet, at least partiallyencompassing the plate stack, or a cast part or a plastic part and has asealing surface for connection to the connector. This has the advantagethat the flange can be mounted directly at an opening, for example, inthe coolant collecting strip, without additional tubing being necessary,which can signify a cost reduction and a simple assembly.

In an embodiment, the heat exchanger can be fabricated at leastpartially from an austenitic and/or ferritic material. An austeniticmaterial has the advantage of excellent corrosion resistance andformability and a ferritic material has the advantage that it iseconomical and the price/performance ratio is very good. It has betterheat conduction and thereby an increased cooling performance, and alower thermal expansion and thereby lower thermal stress.

It is also expedient, if all structural parts of the heat exchanger canbe soldered in a single pass through the furnace. This brings about ahigh dimensional stability due to the minor distortions and forms thebasis for a cost-effective fabrication.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus, are not limitiveof the present invention, and wherein:

FIG. 1 shows an exemplary embodiment of a heat exchanger of theinvention;

FIGS. 2 a to 2 e show a detailed illustration of the exemplaryembodiment of the heat exchanger of the invention;

FIG. 3 a shows a perspective view of a first, bottom plate of a platepair;

FIG. 3 b shows an enlarged perspective view of a first, bottom plate ofa plate pair;

FIG. 4 a shows a perspective view of a second, top plate of a platepair;

FIG. 4 b shows an enlarged perspective view of a second, top plate of aplate pair;

FIG. 5 shows a view of a section through the heat exchanger;

FIG. 6 a shows a perspective view of an end region of the plate stack ofthe heat exchanger;

FIG. 6 b shows a view of the plate stack of the heat exchanger;

FIG. 7 a shows a section through an exemplary embodiment of a platepair;

FIG. 7 b shows a section through a further exemplary embodiment of aplate pair;

FIG. 7 c shows a section through a further exemplary embodiment of aplate pair;

FIG. 7 d shows a section through a further exemplary embodiment of aplate pair;

FIG. 7 e shows a section through a further exemplary embodiment of aplate pair;

FIG. 7 f shows a section through a further exemplary embodiment of aplate pair;

FIG. 8 a shows a view of a plate stack; and

FIG. 8 b shows a view of a plate stack with a connecting flange.

DETAILED DESCRIPTION

FIG. 1 shows an exemplary embodiment of a heat exchanger 1 of theinvention, which can be formed as an exhaust gas cooler or as a chargeair cooler. Alternatively, heat exchanger 1 can also be used in anotherway. It is advantageous if a gaseous fluid is used as a first fluid. Inthis case, exhaust gas or air, such as charge air, can be used as thefirst gaseous fluid. It is also advantageous if a liquid fluid is usedas the second fluid. Water or a water-based mixture used as a coolant oranother coolant or a refrigerant can be employed for this purpose.

Such a heat exchanger 1 can be used advantageously as an exhaust gasheat exchanger in a motor vehicle. Within the scope of a so-calledexhaust gas recirculation system (EGR system), the exhaust gasdischarged from the internal combustion engine of the motor vehicle canbe cooled at least partially by a liquid coolant of a coolant circuit inthe heat exchanger and be again supplied to the intake tract of theinternal combustion engine. Such a heat exchanger 1 can likewise be usedadvantageously as a charge air cooler in a motor vehicle. In this case,the charge air is cooled by the coolant.

Heat exchanger 1 includes a stack 2 of elongated plate pairs 32, wherebyin each case two plates 18, 18′, lying one above the other, are solderedtogether along their longitudinal extension at their rim in thelongitudinal direction.

If plate pairs 32, formed from plates 18, 18′, are stacked one on top ofthe other, a first fluid channel 30 thus forms between the respectiveplate pairs 32. In this regard, first fluid channel 30 is formed betweena top plate 18′ of a bottom plate pair 32 and bottom plate 18 of a topplate pair 32. In this regard, a second fluid channel 4 is formedbetween the two plates 18, 18′ of a plate pair 32. First fluid channel30 is used for the throughflow of the gaseous first fluid, wherebysecond fluid channel 4 is used for the throughflow of the liquid secondfluid.

The plate composite of the two plates 18, 18′ is made open on narrowside 21, as a result which an inlet 5 or outlet 6 is formed for thefirst fluid of the first fluid channel. In this regard, the two platesare connected on the narrow sides such that the second fluid channelbetween the two plates 18, 18′ is closed by an embossing, folding,and/or soldering.

The plate pair of plates 18, 18′ has an approximately U-shaped contourwith a rectangle-like exterior form, whereby plates 18, 18′ areconnected together at two longitudinal rims and/or at two longitudinalsides, e.g., are soldered, whereby the plates in the soldered state areformed spaced apart from one another in a central region.

A coolant conducting arrangement 3, formed flat or lying on the base ofbottom plate 18, can be integrated into the interior of each plate pair32 of plates 18, 18′. Alternatively, this can also be omitted. Saidcoolant conducting arrangement 3 can thereby be embossed as an embossingor embossings in base 60 of plate 18 and/or in base 61 of plate 18′, sothat the fluid flowing through fluid channel 4 formed in the interior ofplate pair 18, 18′ experiences being guided and optionally a channeling.To this end, for example, web-shaped embossings are provided, whichproject into second fluid channel 4 between the two plates 18, 18′.Alternatively, coolant conducting arrangement 3 can also be disposedbetween plates 18, 18′ as a separate part with embossings or structures.Base 60, 61 of plate 18 or 18′ is thereby defined as the substantiallyplanar or flat region between optionally present upright rims of a plate18, 18′.

First fluid channel 30 is arranged between a plate 18′, placed at thetop, of the one plate pair 32 and a plate 18, adjacent thereto, of afurther adjacent plate pair 32. For example, exhaust gas or charge airflows as the first fluid through said fluid channel 30. Second fluidchannel 4 in this case is arranged between the two plates 18, 18′ of aplate pair 32. For example, a liquid coolant flows through said fluidchannel 4.

The first fluid is supplied to first fluid channels 30, therefore, forexample, exhaust gas, via inlet 5 of plate stack 2, which is formed byan open end of narrow side section 21 of plate pairs 32 of plates 18,18′. The first fluid flows through first fluid channel 30 and leavesplate stack 2 of plate pairs 32 with plates 18, 18′ via outlet 6, whichis formed opposite to inlet 5.

An alternative exemplary embodiment can also provide a U-flow throughplate stack 32, so that outlet 6 and inlet 5 are arranged on the sameside of plate stack 2 and a redirection is provided at the end of platepairs 32 with plates 18, 18′, said end being opposite to said inlets andoutlets 5, 6.

Coolant channel arrangement 3 has a plurality of coolant-conducting webs7, which run parallel to one another in the longitudinal direction ofplates 18, and form the individual subchannels, whose open ends, closeto inlet 5 or outlet 6 of the first fluid, are made running in adirection perpendicular to inlet 5 or outlet 6. Said webs guide thesubchannels arranged therebetween to the inlet or outlet for the secondfluid, provided as openings 9, 10 in the side walls or rims 8 of plate18.

Each plate 18 in its longitudinal extension has on both sides anupwardly bent rim 8 in the form of a fold, which extends perpendicularin the direction of the overlying, identically formed adjacent plate 18;see FIG. 2 c on this point.

Plate 18′ likewise has an upright rim 40 on both sides, which isupwardly bent in the manner of a fold, whereby the rim is again bentdownward outwardly to the side. As a result, rim 40 is formed virtuallydouble-layered, whereby a space is provided between the two layers 41,42. Plate 18′ lies on plate 18 and rims 40 lie between rims 8. In sodoing, advantageously the outer walls of rims 40 or 8 are in contact,therefore layer 41 with rim 8.

Depending on the required cooling performance, a plurality of suchconnected plate pairs 32 with plates 18, 18′ can be stacked one abovethe other as plate stack 2.

An opening 9 or 10 in each case in the longitudinal direction of platepairs 32 is incorporated into the end region of the merged ends ofplates 18, 18′ in rim 8 of plate 18. Said openings 9, 10 are used forthe outlet or inlet for the second fluid, such as the coolant. Theopenings of the particular plate pairs are arranged lying one above theother in plate stack 2. Openings 9 or 10, lying one above the other, ofa plurality of plate pairs 32 of plates 18, 18′ are completely coveredby a coolant collecting channel 11, 12 and fluidically connected. Inthis regard, the particular coolant collecting channel 11, 12 can have arecess (not shown further), which sealingly covers openings 9 or 10. Inthis case, coolant collecting channel 11, 12 is advantageously made as adeep-drawn part or a tube segment and is pushed over openings 9 or 10 ofplates 18.

Plate stack 2 is gripped by a frame 13, 14 on narrow side 21. Plates 18are shaped furthermore on narrow sides 21 of plate stack 2 so thatwithout or optionally together with frame 13, 14 a continuouscircumferential contour arises, over which a diffuser 50, a flange, oran adapter can be pushed and soldered leak-free. As an alternative tothe configuration of frames 13, 14, these can also be formed with a holepattern corresponding to the spaced apart fluid channels.

It is advantageous, further, if on at least one or both frames aconnection is provided for carrying the gas and/or tensionor forfixation after the joining.

Heat exchanger 1 ends on the top side with a rimless or rimmed coverplate 19. Said cover plate 19 can lie on rim 8 or between the rims ofthe topmost plate 18 or both plates 18, 18′. Topmost fluid channel 30,particularly as a coolant channel, is closed via the cover plate 19,without additional structural elements being necessary.

On the bottom side, a likewise rimless base plate 20 is used tostabilize the last bottom plate 18.

Second fluid channel 4 is formed, for example, U-shaped between the twoplates 18, 18′. In this regard, fluid channel 4 occupies a firstsubregion 53, which is formed virtually planar and runs substantiallyparallel to base 60 of plate 18. Further, fluid channel 30 occupies twolateral subregions 51, 52, which are oriented substantiallyperpendicular to the plane of base 60 of plate 18. Subregions 51, 52 arethereby configured so that fluid channel 30 is positioned higher at therims than in middle subregion 53 of base 60 of plate 18.

If a further identical plate pair 32 is placed on this plate pair 32,configured in such a way, bottom plate 18 of top plate pair 32 thuscloses first fluid channel 30 between the bottom and top plate pair 32by lying on rims 8 of bottom plates 18 and/or top plate 18′ of bottomplate pair 32.

FIG. 2 shows details of heat exchanger 1, as it is illustrated inFIG. 1. An assembled heat exchanger 1 of the invention, in which platestack 2 is held by clamps 15 running perpendicular to plates 18, 18′, isshown in FIG. 2 a. A diffuser as a collector 16, 17 is placed on eachinlet 5 and outlet 6 for the first fluid such as, for example, anexhaust gas or charge air, whereby two headers 11 or 12 for the secondfluid such as, for example, a coolant, are arranged on the same side ofplate stack 2 near a collector 16, 17. As an alternative, both headers11, 12 can also be arranged on opposite side surfaces of the platestack. This would mean that one header 11, 12 is arranged to the rightof plate stack 2 in the flow direction of the first fluid and one ofheaders 12, 11 to the left of plate stack 2 from the perspective of theflow direction of the first fluid.

FIGS. 2 b and 2 c show a detail of heat exchanger 1, particularly in thearea of outlet 6 for the first fluid. To explain the structure of theheat exchanger, turbulators 22 are shown arranged in fluid channel 4.Turbulators 22, also called fins or corrugated fins, are positioned onplate 18′ and are covered by overlying plate 18, which sits on rims 8,formed perpendicular from underlying plate 18 and/or from plate 18′, andis soldered to it.

Openings 10 are arranged in rim 8 along the longitudinal extension ofrims 8, whereby openings 10 take on approximately the height of rim 8.In this case, the openings are arranged upwardly offset removed by thewidth of a web from the base of plate 18. A web is also arranged abovethe opening up to the top edge of rim 8, so that the opening isdelimited by a web upwardly and downward and is likewise delimited bythe material of rim 8 to the side from the perspective in the directionof flow of the first fluid.

In FIG. 2 c, joined plates 18 and 18′ can be seen, which form the secondfluid channel in a U-shape between them.

Coolant collecting channel 12 extending over openings 10, apart from thefunction of coolant conduction, can also be used as a tensioning clampas a replacement for the soldering device or for a weight support duringsoldering. Other functions, such as the attachment of pipes in theengine periphery or hold points for the radiator, can also be integratedin coolant collecting channel 12; see FIG. 2 d.

In proposed heat exchanger 1, second fluid channels 30, particularly ascoolant channels, are formed alternately to first fluid channels 4,particularly as exhaust gas channels. Second fluid channels 30 in thiscase are formed U-shaped in section and enclose first fluid channels 4on three sides, so that first fluid channels 4 can be cooled from threesides by the fluid of the second fluid channel. Further, the secondfluid channel of the overlying plate pair delimits the first fluidchannel, so that the adjacent second fluid channel delimits the fourthside of the first fluid channel and the fluid flowing through it coolsthe first fluid channel. Plates 18, 18′ are configured so that alongitudinal soldering occurs either at a largely lateral soldering seamor vertically on the already explained internally formed rim 8 of plates18, 18′.

In contrast to the prior art, rim 8 protrudes substantiallyperpendicular to the base of plates 18, 18′ of the plate pair and thusallows the second fluid channel, particularly for the coolant, to bedelimited outwardly, so that the outer wall of the heat exchanger is incontact with the second fluid, particularly the coolant. The outer wallthus can be formed cooled, which is of great advantage for thesurrounding area of the heat exchanger, because the surrounding areadoes not become as hot as the first fluid. Furthermore, a smooth lateralsurface on plate stack 2 is formed by the lateral contour of rim 8, sothat, firstly, the headers can be attached and sealed well and the platestack can be enclosed well and thereby braced. Good leak tightnessduring soldering is achieved thereby.

FIGS. 3 a and 3 b show a bottom plate 18 of the plate pair. In thisregard, the plate has an approximately rectangular elongated contour. Arim 8, which protrudes approximately at a right angle from the base orfrom the plane of base 60, is bent upwardly at the two opposite lateralsides of plate 18. Openings 10 are introduced in a rim 8 at the ends oradjacent to the ends of the plate for the inflow or outflow of a fluid.Openings 10 are made substantially rectangular.

Webs 7, which are used to create subchannels and form a flow pathbetween openings 10, are embossed in base 60 as a coolant conductingarrangement 3. In this regard, individual webs 7 or webs 7 are formedsuch that they have a rectangular course from the one opening 10 to theother opening 10. In a first section, they run perpendicular to mainorientation 90 of plate 18, in a middle section they run parallel tomain orientation 90 of plate 18, and in a further section they again runperpendicular to main orientation 90 of plate 18.

Second webs 7′, which only have an orientation parallel to mainorientation 90, can also be arranged between webs 7 formed in such away.

FIGS. 4 a and 4 b show a top plate 18′ of the plate pair. In thisregard, plate 18′ has an approximately rectangular elongated contour. Arim 8′, which protrudes approximately at a right angle from the base orfrom the plane of base 61, is bent upwardly at the two opposite lateralsides of plate 18′. In this case, rim 8′ is made double-walled. Openings10′ are introduced in the outer rim sheet of rim 8′ at the ends oradjacent to the ends of plate 18′ for the inflow or outflow of a fluid.Openings 10′ are made substantially rectangular.

Base 61 is formed planar or it can have webs, extending downward intothe second fluid channel, or other embossings.

On the front and back end region of plate 18′, the base and the rims areshaped such that a sealed end region forms when plate 18′ is placed onplate 18.

If plate 18′ is placed on plate 18, second fluid channel 4 thus arisesbetween the two plates 18, 18′. The two plates 18, 18′ are connectedsealed to one another except for openings 10.

FIG. 5 shows a section through heat exchanger 1, which is formed by thestacking of plate pairs 32 on top of one another. In this case, theplate pairs are formed by plates 18 and 18′. Fluid channel 4 is formedbetween a bottom plate 18 and a top plate 18′, particularly for thethroughflow of a coolant. First fluid channel 30 is arranged between atop plate 18′ of a plate pair 32 and bottom plate 18 of an adjacentplate pair.

A turbulence insert 22 can be provided in first fluid channel 30.

It is evident in FIG. 5 that second fluid channel 4 surrounds firstfluid channel 30. Second fluid channels 4, which delimit the stackoutwardly, are arranged on the sides of stack 2.

FIGS. 6 a and 6 b show an end region of stack 2 of plate pairs 32. Inthis case, only first fluid channels 30 can be seen, because the secondfluid channels are closed by the folding or embossing of plates 18′ inthe end region thereof.

FIGS. 7 a to 7 f show variations of plate pairs 32 in a sectional view.

FIG. 7 a shows a section through a plate pair 32 according to thepreceding figures. Plate 18 as the bottom plate of plate pair 32 isformed substantially U-shaped with a planar base 60 and rims 8protruding approximately at right angles thereto. Plate 18′ is likewiseformed approximately U-shaped with a planar base 61 and upright rims 8′.In this case, rims 8′ are made double-walled with an inner wall region70 and an outer wall region 71 and a top connecting wall 72. Outer wallregion 71 is inwardly adjacent to rim 8 of plate 18, whereby rims 8′ arearranged between rims 8. Second fluid channel 4 is formed between thetwo plates 18, 18′. The first fluid channel is formed above base 61 andbetween opposite rims 8′, when two plate pairs lie one on top ofanother.

FIG. 7 b shows a section through an alternative plate pair. Plate 18 asthe bottom plate of plate pair 32 is formed substantially U-shaped witha planar base 60 and rims 8 protruding approximately at right anglesthereto. Plate 18′ is likewise formed approximately U-shaped with aplanar base 61 and upright rims 8′. In this case, rims 8′ are madedouble-walled with an inner wall region 70 and an outer wall region 71and a top connecting wall 72. Outer wall region 71 is outwardly adjacentto rim 8 of plate 18. Rim 8′ partially overlaps rim 8 in this case.Second fluid channel 4 is formed between the two plates 18, 18′. Thefirst fluid channel is formed above base 61 and between opposite rims8′, when two plate pairs lie one on top of another.

FIG. 7 c shows a section through a further alternative plate pair 32.Plate 18 as the bottom plate of plate pair 32 is formed substantiallyflush with a planar base 60. Plate 18′ is formed approximately U-shapedwith a planar base 61 and upright rims 8′. In this case, rims 8′ aremade double-walled with an inner wall region 70 and an outer wall region71 and a top connecting wall 72. The outer wall has at the bottom aninwardly pointing further wall region 73, which lies on planar base 60of plate 18. Second fluid channel 4 is formed between the two plates 18,18′. The first fluid channel is formed above base 61 and betweenopposite rims 8′, when two plate pairs lie one on top of another.

FIG. 7 d shows a section through a further alternative plate pair 32.Plate 18 as the bottom plate of plate pair 32 is formed substantiallyflat with a planar base 60. Plate 18′ is formed approximately U-shapedwith a planar base 61 and upright rims 8′. In this case, rims 8′ aremade double-walled with an inner wall region 70 and an outer wall region71 and a top connecting wall 72. The outer wall has at the bottom aninwardly pointing further wall region 73, which reaches under planarbase 60 of plate 18 and is adjacent to it from below. Second fluidchannel 4 is formed between the two plates 18, 18′. The first fluidchannel is formed above base 61 and between opposite rims 8′, when twoplate pairs lie one on top of another.

FIG. 7 e shows a section through a further alternative plate pair 32.Plate 18 as the bottom plate of plate pair 32 is formed substantiallyU-shaped with a planar base 60 and rims 8 protruding approximately atright angles thereto. Plate 18′ is likewise formed approximatelyU-shaped with a planar base 61 and upright rims 8′. In this case, rims8′ are made double-walled with an inner wall region 70 and an outer wallregion 71 and a top connecting wall 72. Outer wall region 71 at itsbottom region has a bent-off section 74 which is inwardly adjacent torim 8 of plate 18. Second fluid channel 4 is formed between the twoplates 18, 18′. The first fluid channel is formed above base 61 andbetween opposite rims 8′, when two plate pairs lie one on top ofanother.

FIG. 7 f shows a section through a further alternative plate pair 32.Plate 18 as the bottom plate of plate pair 32 is formed substantiallyU-shaped with a planar base 60 and rims 8 protruding approximately atright angles thereto. Plate 18′ is likewise formed approximatelyU-shaped with a planar base 61 and upright rims 8′. In this case, rims8′ are made double-walled with an inner wall region 70 and an outer wallregion 71 and a top connecting wall 72. Rim 8 at its top region has abent-off section 75, which is inwardly adjacent to wall region 71 ofplate 18′. Second fluid channel 4 is formed between the two plates 18,18′. The first fluid channel is formed above base 61 and betweenopposite rims 8′, when two plate pairs lie one on top of another.

Special designs of exhaust gas heat exchanger 1 of the invention will bedescribed below, which are not shown in greater detail in the drawings.An I-flow, therefore a linear throughflow, for two coolant circuits willbe considered first. In this case, the plates have in addition two sideinlets or outlets before or after a partitioning of a coolant channelbetween the front and back part of the coolant channel. This type ofdesign is especially suitable for applications with a high-temperatureand low-temperature coolant circuit. The partitioning of the coolantchannel can occur in a completely sealing manner or with a small leakageamount between the high-temperature and low-temperature coolant sectionbeing allowed. If required, more than two coolant circuits can also beformed analogously.

In the case of a U-flow, therefore with a redirected throughflow,instead of a diffuser a closed box is disposed at the redirection end,whereby on the inlet side for the first fluid, therefore the exhaustgas, the sealing of the flows occurs by the construction of a partingplane in the form of a metal sheet or a cast wall between the inlet andoutlet for the first fluid in the area of the front edge of a fluidchannel for the second fluid, whereby optionally small leakage amountsof the first fluid could be allowed. Alternatively, the flows in eachexhaust gas channel can be separated by a continuous fin, for example, asmooth fin, a corrugated or dimpled fin without cut webs, or by apartition plate inserted in each plane in the web fin. The sealingbetween the two flows then occurs directly on the fin, whereby theparting plane must accommodate the fins or the plate contour of theplate stack. A partition plate inserted in the fin in this case can alsoaccommodate the plate contour, so that the parting plane between theinlet and outlet of the exhaust gas can be designed simpler in geometricterms.

A U-flow with two coolant circuits is achieved when the mounted coolantheader tanks contain a partition wall that divides the coolant headertanks into two segments each at the particular end. The supplying ordischarging of the coolant from the one or other circuit occurs in onesegment. Alternatively, the two coolant header tanks can be placed oneabove the other. Further, the slitting of the coolant channels can occurfor the high-temperature circuit on the one side of the exhaust gas heatexchanger and for the low-temperature circuit on the respective otherside of the exhaust gas heat exchanger. In sum, four coolant header tankare then needed for the entry and exiting of the two media. Finally, theoptions can be combined, because a combined tank with a partition wallis arranged at one end of the exhaust gas heat exchanger and at theother end separated coolant header tanks are arranged on the two sidesof the exhaust gas heat exchanger. Here as well, more than two coolantcircuits can be formed analogously if necessary.

In the design of two parallel coolant circuits, the coolant channel isseparated longitudinally by corrugations into two or more flowssealingly or with a small leakage being allowed; a medium can beconducted through the corrugations in a U-shaped manner or in ameandering manner in a plurality of loops. The second flows in this casecan also be operated with two different media, because a separate supplyof the flows from one or the other side of the exhaust gas cooler ispossible.

Based on the explained solution, a lower-weight and structurally simplerarrangement of the exhaust gas heat exchanger or of the charge aircooler, which has a high thermal capacity, is possible.

FIG. 8 a shows a detail of a heat exchanger 1. A heat exchanger 1 of theinvention, in which plate stack 2 is constructed of plates 18, 18′, isshown in FIG. 8 a.

FIG. 8 a shows a detail of heat exchanger 1, particularly in the area ofoutlet 6 for the first fluid. To explain the structure of the heatexchanger, turbulators 22 are shown arranged in fluid channel 4.Turbulators 22, also called fins or corrugated fins, are positioned onplate 18′ and are covered by overlying plate 18, which sits on rims 8,formed perpendicular from underlying plate 18 and/or from plate 18′, andis soldered to it.

Openings 10 are arranged in rim 8 along the longitudinal extension ofrims 8, whereby openings 10 take on approximately the height of rim 8.In this case, the openings are arranged upwardly offset removed by thewidth of a web from the base of plate 18. A web is also arranged abovethe opening up to the top edge of rim 8, so that the opening isdelimited by a web upwardly and downward and is likewise delimited bythe material of rim 8 to the side from the perspective in the directionof flow of the first fluid.

FIG. 8 b shows plate stack 2, in which a bent metal sheet is provided asa connecting flange 100. The bent metal sheet 100 is formed as U-shapedsheet with a top and bottom end-side section 102, 103, whereby a middlesection 104, which has window 101, is provided between these twoend-side sections 102, 103. Said window 101 is arranged in such a waythat it communicates with openings 10. Arrow 110 indicates the gas entryinto fluid channels 4 and arrow 111 indicates the coolant entry or exitthrough window 101.

Window 101 is surrounded by a frame 120, which is preferably formed flatand is formed as a contact surface for a vehicle-side coolant connectionand functions as a sealing surface.

The connecting flange can be made as a bent metal sheet part oralternatively also a cast part or the like.

It is advantageous, if there is a material connection between thediffuser and coolant tank on the gas inlet side. This brings aboutthermal relief.

It is also advantageous, if there is a material connection between thediffuser and radiator matrix, therefore fluid channels 4, on all sideswith the exception of the coolant tank side.

It is also advantageous, if in the case of overlapping of walls the wallthickness of the materials and metal sheets can be reduced. In thisregard, a wall metal sheet thickness from 0.2 mm to 0.5 mm, preferably0.2 mm to 0.3 mm, can be provided.

The height of the coolant channel as a fluid channel is preferably lessor equal to 2 mm.

The distance between corrugations 7, particularly in the fluid channel,is preferably less or equal to 3 mm to 15 mm, preferably 4 mm to 8 mm.

It is also advantageous, if the first and/or second fluid channel has aturbulence insert. A turbulence insert is used to increase performanceand/or to increase strength and to serve as a support in the solderingprocess.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are to beincluded within the scope of the following claims.

What is claimed is:
 1. A heat exchanger comprising: a plate stack havinga plurality of elongated plate pairs, wherein two interconnected platesform a second fluid channel between the two interconnected plates; and afirst fluid channel formed between two plate pairs, the first fluidchannel being surrounded by two second fluid channels, each second fluidchannel being connected to at least one coolant collecting channel. 2.The heat exchanger according to claim 1, wherein the interconnected twoplates of a plate pair form a U-shaped second fluid channel or aZ-shaped second fluid channel between them.
 3. The heat exchangeraccording to claim 1, wherein the U-shaped second fluid channel iscovered by a further second fluid channel such that a first fluidchannel is located between the two second fluid channels.
 4. The heatexchanger according to claim 1, wherein the first fluid channel isenclosed on four sides by the second fluid channel.
 5. The heatexchanger according to claim 1, wherein a wall of the second fluidchannel delimits the heat exchanger outwardly.
 6. The heat exchangeraccording to claim 1, wherein the two interconnected plates of a platepair are soldered or welded on both sides at their rims along theirlongitudinal extension or transverse extension.
 7. The heat exchangeraccording to claim 1, wherein a rim formed perpendicular on the bottomplate or on the top plate is soldered to a base of the overlying bottomplate.
 8. The heat exchanger according to claim 1, wherein at least oneopening for connecting the second fluid channel to the coolantcollecting channel is formed in at least one of the formed rims.
 9. Theheat exchanger according to claim 1, wherein one opening each is formedin the rim of the plate near an inlet and an outlet for the first fluid,wherein the inlet and the outlet for the first fluid are formed bynarrow sides of the two interconnected plates, and wherein the openingsof a plurality of interconnected plate pairs, arranged lying on top ofone another, lie approximately one above the other.
 10. The heatexchanger according to claim 1, wherein a rimless or rimmed cover plateis provided for closing the topmost second fluid channel.
 11. The heatexchanger according to claim 1, wherein the coolant collecting channelis formed as a header.
 12. The heat exchanger according to claim 11,wherein the header extends such that the header covers the plate stackapproximately perpendicularly and has a recess for exchanging the secondfluid or a coolant, opposite to the openings of the plate stack.
 13. Theheat exchanger according to claim 11, wherein the header is formed as atube segment.
 14. The heat exchanger according to claim 11, wherein theheader encompasses the plate stack at least partially as a tensioningclamp.
 15. The heat exchanger according to claim 1, wherein the coolantcollecting channel is formed as a coolant tank.
 16. The heat exchangeraccording to claim 15, wherein each second fluid channel is connected tothe coolant tank, and wherein the coolant tank has an outer connectionfor a connector for supplying the coolant to the coolant tank or fordischarging the coolant from the coolant tank.
 17. The heat exchangeraccording to claim 16, wherein the coolant tank is formed as a one-piecediffuser.
 18. The heat exchanger according to claim 1, wherein thecoolant collecting channel is shaped as a flange, which is formed from ametal sheet, at least partially encompassing the plate stack, or a castpart or a plastic part and has a sealing surface for connection to theconnector.
 19. The heat exchanger according to claim 1, wherein the heatexchanger is fabricated at least partially of an austenitic and/orferritic material.
 20. The heat exchanger according to claim 1, whereinall structural parts of the heat exchanger are solderable in a singlepass through the furnace.
 21. The heat exchanger according to claim 1,wherein the heat exchanger is an exhaust gas cooler or charge aircooler.